// tslint:disable no-console

export enum Level {
	Trace,
	Debug,
	Info,
	Warning,
	Error,
}

export class Field<T> {
	public constructor(
		public readonly identifier: string,
		public readonly value: T,
	) { }

	public toJSON(): object {
		return {
			identifier: this.identifier,
			value: this.value,
		};
	}
}

export class Time {
	public constructor(
		public readonly expected: number,
		public readonly ms: number,
	) { }
}

export type Argument = any; // tslint:disable-line no-any

/**
 * `undefined` is allowed to make it easier to conditionally display a field.
 * For example: `error && field("error", error)`
 */
export type FieldArray = Array<Field<Argument> | undefined>;

/**
 * Functions can be used to remove the need to perform operations when the
 * logging level won't output the result anyway.
 */
export type LogCallback = () => [string, ...FieldArray];

export const time = (expected: number): Time => {
	return new Time(expected, Date.now());
};

export const field = <T>(name: string, value: T): Field<T> => {
	return new Field(name, value);
};

export type Extender = (msg: {
	message: string,
	level: Level,
	type: "trace" | "info" | "warn" | "debug" | "error",
	fields?: FieldArray,
	section?: string,
}) => void;

/**
 * Format and build a *single* log entry at a time.
 */
export abstract class Formatter {
	private format = "";
	private args = <string[]>[];
	private fields = <Field<Argument>[]>[];
	private readonly minimumTagWidth = 5;

	/**
	 * formatType is used for the strings returned from style() and reset().
	 */
	public constructor(
		private readonly formatType: string = "%s",
		private readonly colors: boolean = true,
	) {}

	/**
	 * Add a tag.
	 */
	public tag(name: string, color: string): void {
		for (let i = name.length; i < this.minimumTagWidth; ++i) {
			name += " ";
		}
		this.push(name + " ", color);
	}

	/**
	 * Add a field or an argument. Arguments will display inline in the order they
	 * were pushed. Fields will display differently based on the formatter. Fields
	 * cannot have custom colors.
	 */
	public push(fields: Field<Argument>[]): void;
	public push(arg: Argument, color?: string, weight?: string): void;
	public push(arg: Argument | Field<Argument>[], color?: string, weight?: string): void {
		if (Array.isArray(arg) && arg.every((a) => a instanceof Field)) {
			return void this.fields.push(...arg);
		}
		if (this.colors) {
			this.format += `${this.formatType}${this.getType(arg)}${this.formatType}`;
			this.args.push(this.style(color, weight), arg, this.reset());
		} else {
			this.format += `${this.getType(arg)}`;
			this.args.push(arg);
		}
	}

	/**
	 * Write everything out and reset state.
	 */
	public write(): void {
		this.doWrite(...this.flush());
	}

	/**
	 * Return current values and reset state.
	 */
	protected flush(): [string, string[], Field<Argument>[]] {
		const args = [this.format, this.args, this.fields] as [string, string[], Field<Argument>[]];
		this.format = "";
		this.args = [];
		this.fields = [];
		return args;
	}

	/**
	 * Return a string that applies the specified color and weight.
	 */
	protected abstract style(color?: string, weight?: string): string;

	/**
	 * Return a string that resets all styles.
	 */
	protected abstract reset(): string;

	/**
	 * Write everything out.
	 */
	protected abstract doWrite(format: string, args: string[], fields: Field<Argument>[]): void;

	/**
	 * Get the format string for the value type.
	 */
	private getType(arg: Argument): string {
		switch (typeof arg) {
			case "object": return "%o";
			case "number": return "%d";
			default: return "%s";
		}
	}
}

/**
 * Display logs in the browser using CSS in the output. Fields are displayed on
 * individual lines within a group.
 */
export class BrowserFormatter extends Formatter {
	public constructor() {
		super("%c");
	}

	protected style(color?: string, weight?: string): string {
		return (color ? `color: ${color};` : "")
			+ (weight ? `font-weight: ${weight};` : "");
	}

	protected reset(): string {
		return this.style("inherit", "normal");
	}

	public doWrite(format: string, args: string[], fields: Array<Field<Argument>>): void {
		console.groupCollapsed(format, ...args);
		fields.forEach((field) => {
			this.push(field.identifier, "#3794ff", "bold");
			if (typeof field.value !== "undefined" && field.value.constructor && field.value.constructor.name) {
				this.push(` (${field.value.constructor.name})`);
			}
			this.push(": ");
			this.push(field.value);
			const flushed = this.flush();
			console.log(flushed[0], ...flushed[1]);
		});
		console.groupEnd();
	}
}

/**
 * Display logs on the command line using ANSI color codes. Fields are displayed
 * in a single stringified object inline.
 */
export class ServerFormatter extends Formatter {
	public constructor() {
		super("%s", !!process.stdout.isTTY);
	}

	protected style(color?: string, weight?: string): string {
		return (weight === "bold" ? "\u001B[1m" : "")
			+ (color ? this.hex(color) : "");
	}

	protected reset(): string {
		return "\u001B[0m";
	}

	private hex(hex: string): string {
		const [r, g, b] = this.hexToRgb(hex);
		return `\u001B[38;2;${r};${g};${b}m`;
	}

	private hexToRgb(hex: string): [number, number, number] {
		const integer = parseInt(hex.substr(1), 16);
		return [
			(integer >> 16) & 0xFF,
			(integer >> 8) & 0xFF,
			integer & 0xFF,
		];
	}

	protected doWrite(format: string, args: string[], fields: Array<Field<Argument>>): void {
		if (fields.length === 0) {
			return console.log(
				"[%s] " + format,
				new Date().toISOString(),
				...args
			);
		}
		const obj: { [key: string]: Argument} = {};
		fields.forEach((field) => obj[field.identifier] = field.value);
		console.log(
			"[%s] " + format + " %s%s%s",
			new Date().toISOString(),
			...args,
			this.style("#8c8c8c"), JSON.stringify(obj), this.reset(),
		);
	}
}

export class Logger {
	public level = Level.Info;

	private readonly nameColor?: string;
	private muted: boolean = false;

	public constructor(
		private _formatter: Formatter,
		private readonly name?: string,
		private readonly defaultFields?: FieldArray,
		private readonly extenders: Extender[] = [],
	) {
		if (name) {
			this.nameColor = this.hashStringToColor(name);
		}
		if (typeof process !== "undefined" && typeof process.env !== "undefined") {
			switch (process.env.LOG_LEVEL) {
				case "trace": this.level = Level.Trace; break;
				case "debug": this.level = Level.Debug; break;
				case "info": this.level = Level.Info; break;
				case "warn": this.level = Level.Warning; break;
				case "error": this.level = Level.Error; break;
			}
		}
	}

	public set formatter(formatter: Formatter) {
		this._formatter = formatter;
	}

	/**
	 * Supresses all output
	 */
	public mute(): void {
		this.muted = true;
	}

	public extend(extender: Extender): void {
		this.extenders.push(extender);
	}

	public info(fn: LogCallback): void;
	public info(message: string, ...fields: FieldArray): void;
	public info(message: LogCallback | string, ...fields: FieldArray): void {
		this.handle({
			type: "info",
			message,
			fields,
			tagColor: "#008FBF",
			level: Level.Info,
		});
	}

	public warn(fn: LogCallback): void;
	public warn(message: string, ...fields: FieldArray): void;
	public warn(message: LogCallback | string, ...fields: FieldArray): void {
		this.handle({
			type: "warn",
			message,
			fields,
			tagColor: "#FF9D00",
			level: Level.Warning,
		});
	}

	public trace(fn: LogCallback): void;
	public trace(message: string, ...fields: FieldArray): void;
	public trace(message: LogCallback | string, ...fields: FieldArray): void {
		this.handle({
			type: "trace",
			message,
			fields,
			tagColor: "#888888",
			level: Level.Trace,
		});
	}

	public debug(fn: LogCallback): void;
	public debug(message: string, ...fields: FieldArray): void;
	public debug(message: LogCallback | string, ...fields: FieldArray): void {
		this.handle({
			type: "debug",
			message,
			fields,
			tagColor: "#84009E",
			level: Level.Debug,
		});
	}

	public error(fn: LogCallback): void;
	public error(message: string, ...fields: FieldArray): void;
	public error(message: LogCallback | string, ...fields: FieldArray): void {
		this.handle({
			type: "error",
			message,
			fields,
			tagColor: "#B00000",
			level: Level.Error,
		});
	}

	/**
	 * Returns a sub-logger with a name.
	 * Each name is deterministically generated a color.
	 */
	public named(name: string, ...fields: FieldArray): Logger {
		const l = new Logger(this._formatter, name, fields, this.extenders);
		if (this.muted) {
			l.mute();
		}
		return l;
	}

	private handle(options: {
		type: "trace" | "info" | "warn" | "debug" | "error";
		message: string | LogCallback;
		fields?: FieldArray;
		level: Level;
		tagColor: string;
	}): void {
		if (this.level > options.level || this.muted) {
			return;
		}

		let passedFields = options.fields || [];
		if (typeof options.message === "function") {
			const values = options.message();
			options.message = values.shift() as string;
			passedFields = values as FieldArray;
		}

		const fields = (this.defaultFields
			? passedFields.filter((f) => !!f).concat(this.defaultFields)
			: passedFields.filter((f) => !!f)) as Array<Field<Argument>>;

		const now = Date.now();
		let times: Array<Field<Time>> = [];
		const hasFields = fields && fields.length > 0;
		if (hasFields) {
			times = fields.filter((f) => f.value instanceof Time);
			this._formatter.push(fields);
		}

		this._formatter.tag(options.type, options.tagColor);
		if (this.name && this.nameColor) {
			this._formatter.tag(this.name, this.nameColor);
		}
		this._formatter.push(options.message);
		if (times.length > 0) {
			times.forEach((time) => {
				const diff = now - time.value.ms;
				const expPer = diff / time.value.expected;
				const min = 125 * (1 - expPer);
				const max = 125 + min;
				const green = expPer < 1 ? max : min;
				const red = expPer >= 1 ? max : min;
				this._formatter.push(` ${time.identifier}=`, "#3794ff");
				this._formatter.push(`${diff}ms`, this.rgbToHex(red > 0 ? red : 0, green > 0 ? green : 0, 0));
			});
		}

		this._formatter.write();

		this.extenders.forEach((extender) => {
			extender({
				section: this.name,
				fields: options.fields,
				level: options.level,
				message: options.message as string,
				type: options.type,
			});
		});
	}

	/**
	 * Hashes a string.
	 */
	private djb2(str: string): number {
		let hash = 5381;
		for (let i = 0; i < str.length; i++) {
			hash = ((hash << 5) + hash) + str.charCodeAt(i); /* hash * 33 + c */
		}
		return hash;
	}

	private rgbToHex(r: number, g: number, b: number): string {
		const integer = ((Math.round(r) & 0xFF) << 16)
			+ ((Math.round(g) & 0xFF) << 8)
			+ (Math.round(b) & 0xFF);
		const str = integer.toString(16);
		return "#" + "000000".substring(str.length) + str;
	}

	/**
	 * Generates a deterministic color from a string using hashing.
	 */
	private hashStringToColor(str: string): string {
		const hash = this.djb2(str);
		return this.rgbToHex(
			(hash & 0xFF0000) >> 16,
			(hash & 0x00FF00) >> 8,
			hash & 0x0000FF,
		);
	}
}

export const logger = new Logger(
	typeof process === "undefined" || typeof process.stdout === "undefined"
		? new BrowserFormatter()
		: new ServerFormatter(),
);